What actually needs to happen is that it needs to be reconfigured. It doesn't need eight lanes and it doesn't need to be widened - what it needs is shoulders and a host of other legitimate safety improvements and you can easily accommodate those in the current profile if you execute a lane drop to six lanes through Dorchester. (I'd want to see a study done to figure out exactly how much mitigation would need to happen if you widened the road by 20' instead of dropping the lane just to prove that it's untenable to anyone who claims "just widen the road!" - 20 feet gets you half-width breakdown lanes and an eight-foot median without a lane drop, but I imagine you're taking something on the order of a hundred properties to get that twenty feet.)
In fact, I'd expect a study to reveal that average throughput on the freeway goes up with a lane drop and shoulders, even as maximum throughput goes down, because the road becomes much more capable of handling adversity.
Absolutely. Though I would argue it does need 8 lanes because of 128 having 8 at Braintree and Reading, 93 north of the Somerville decks having 8, the Pike between Newton and Copley having 8, and the reconfig of Route 3 on final approach to revamped Braintree split likely getting 8 back to Union St. so all the frontage road action and the lane splits/merges at the interchange stay constant-number. That's a big part of the clog...lack of gradual-enough lane drops/pickups to sort all the converging 93/37/Burgin/Furnace Brook/Union/Red Line traffic in that 2.5 mile span.
8 does seem to be the standard for inside-128 and on the final approaches to 128. And north to NH as well (they are planning to fix the Andover-495 pinch + breakdown travel on 93 with an add-a-lane because the carriageways and most bridges are wide enough, and are actively fixing the short Newburyport pinch on 95 with bridge state-of-repair renewal). I wouldn't mess with that since it seems to be working at the interchanges that aren't 50's relics overdue for redesign or at the intersection points of canceled highways.
What fucked it all up on the Expressway was taking the breakdown lanes for the Zipper. That's the great lesson from the 128 reconstruction. Wide, full interstate-standard left + right shoulders absorb disruption so well that flow is optimal and doesn't get hosed by accidents. Really, except for the mangled old interchanges that have to wait in line for megabucks funding--Braintree, Canton, Burlington (not even Weston so much...that's a bigger problem on the Pike than it is 128)--the highway's a really painless drive nowadays despite carrying extremely higher loads post- Big Dig. Not even the Needham pinch still awaiting the final add-a-lane phase is all that bad anymore after the 24-to-109 lane opened. Buffer space and elimination of the breakdown lane travel was that big an improvement. I've found even in low-traffic hours that if there's so much as small debris bouncing around the highway that the confidence the left- + right-lane can swerve a couple feet into the shoulders and make swerving room for the middle 2 lanes to adjust in tandem makes all the difference in the world. You can't swerve on any of lane of the Expressway when there's zero shoulder...you can only slam brakes and wait for an opening, or slam braces and brace yourself for the debris hit. The accident rate and flow correction is so much better on 128, and so much scarier on the Expressway.
What I would do is widen the left + right shoulders on the Expressway to full 128 width and just abolish the zipper. Few feet's widening only on the handful or portions that do have a right breakdown lane and just need help with the left-shoulder width, and some necessary widenings of bridges, etc. elsewhere where both sides are pinched. And you still will have to do the expensive Savin Hill fix with the T tracks. If 128 can handle the loads at full interstate standards, pretty dense exit spacing, and no HOV lanes...the Expressway can do the same. The addition of the HOV did more harm than good, and I'm convinced all these conceptual plans to extend the zipper to Southampton are going to do more harm than good.
The state will never ever ever give up on the HOV experiment, even though abolishing the zipper wouldn't be any real capacity reduction per se. It's just ingrained conventional wisdom that HOV's do...something!...even against the mountain of data that says they have negligible effect on traffic management, increase induced demand, get little compliance (I remember when the I-84 and I-91 HOV's first opened in CT with 3-person occupancy requirements, and were so empty ConnDOT had to lower the limit to 2 to save face), and actually make things worse in constrained situations like the SE Expressway and the Somerville lower deck. It's too much in their DNA.
But that would literally solve it with no capacity loss. The Expressway's problems are 60% structural, 40% artificial.
The important thing that shouldn't be forgotten in any Expressway reconstruction, however, is the extremely fragile rail line(s) that run alongside it. I would want any comprehensive overhaul of the road to take a long hard look at the Red Lines and the Old Colony Line and ask if there's really, truly no way to bring the Old Colony up from single track to an unbroken three between South Station and JFK and an unbroken two until south of Braintree.
The conceptual plans from the MPO suck because they are hellbent on extending that broken zipper lane to Southampton and force the Old Colony to get tunneled for a short stretch at the narrowest point. Which is a humongous waste of funds because RR tunnels have to have much lesser grades on the inclines, diesel exhaust ventilation the closer a tunnel gets to/above a half-mile, and much higher clearances future-proofed for overhead electrification and increasing freight clearances. There's no active freight here today because CSX combines its Port of Quincy pickups in Braintree with its overnight local from Framingham-Attleboro-Middleboro, but there's rumors they may dump the OC south of Braintree to the Mass Coastal shortline that they dished off the South Coast branches to. In which case their overnight pickup route switches to Readville-Braintree and back. This is also the stretch of track that connects Port of Quincy and Port of Southie, so it's reasonable assumption that by 50 years now there's going to be some serious tonnage of port freight coming up from Quincy and heading out to Readville, Framingham, and Worcester lashed up to the Southie pickups.
It's much easier to swing if you do this:
-- Compact Columbia Jct. It's got all that absurd complexity of flyover ramps because the assumption in 1960 when the Braintree Branch was in design was that state's RR network would go completely extinct except for the NEC, B&A, Lowell, and outer Haverhill Lines. So the branch was designed as an outright commuter rail replacement that could go to Brockton, Weymouth, etc. using higher-speed subway rolling stock. That could blast from Andrew to North Quincy at 80 MPH or something (Columbia/JFK wasn't a Braintee stop until '88). Sort of like "HSHRT". Hence the crazy, space-intensive flyovers.
A simple 1<-->2 track split + yard turnout achieves all the grade separation a conventional subway line would need at one-third the sprawl.
Old Colony takes 1 more track in all the freed-up space, 93 takes more on the other side. JFK's commuter rail platform is 12 feet wide per the T's full-high island platform standard spec...that was designed from Day 1 to take kiss-and-ride space to drop down a second track and hook an overhead walkway to the Red fare lobby with little other modification to the station except grafting that CR platform elevator/escalator into to the existing Red overhead walk and maybe doing a divider wall so the CR riders bypass the Charlie gates segregated from Red riders (no extra opportunities for fare evasion). They could arguably do that right this second and create a passing opportunity for a few more slots. Would take DCR's approval to narrow the Old Colony Ave. ramps or flip the sidewalk to the other side if that passing siding were to extend north at all instead of merging right back at slow speed after the platform (that whole parkway warcrime interchange should be nuked from orbit anyway)...but you can do the platform-proper 2nd track right now.
-- (with above) Reconfigure the tracks into JFK so it's 2x2 inbound/outbound at the island platforms instead of 2x2 Ashmont/Braintree. Another space-inefficient relic of the obsolete "HSHRT" plan that got cemented when the Braintree platforms got grafted on 26 years ago.
-- Narrower-profile flyover bridges south of the station since the 2x2 reconfig at Columbia now means only 1 track from 1 branch has to switch sides mid-air with the rest of the sorting happening at-grade. Again...that current flyover is so space-intensive because of 1960's Braintree "HSHRT" that's no longer needed because the commuter rail network survived extinction and came back to serve that mid-distance niche.
-- Braintree-under-Ashmont tunnel. Braintree tunnel slides under the OC tracks at the station to structurally steer clear and position itself to spit out on the correct track side after 93 pulls away.
-- Portal-up the second 93 peels out. Shift the current Ashmont and current Braintree tracks over 3-4 feet on each end of the ROW to create center room for the 2nd OC track out to Clayton St. split, and add 1 more deck berth to the Freeport St. and Park St. overpasses (Freeport might actually have the room for it now if that little gap of daylight between the Ashmont tracks and the OC track were filled in with an extra deck girder).
I did a little MS Paint-quality diagram of the gist of it last year on RR.net showing how the lines would split (JFK end only...underneath Savin Hill to the south portal and Clayton St. is pretty easy to visualize). Tracks on surface are depicted, tracks underground hidden with subway outline...so those Ashmont tracks ride on top of the literal roof of the new Braintree/Savin Hill tunnel. Like...right on top of the bare load-bearing roof concrete; that's how shallow a dig this is.
Crossover locations not-to-scale, but you get the idea. This gives the OC double-track from Southampton to the Wollaston pinch thanks to the mass simplification of Columbia Jct. and the Savin Hill tunneling.
This also has the advantage of combining the electrical feeds and signaling cables for both branches above and below that subway's roof. When the Braintree branch was constructed the whole 1-3/4 miles from the first track splitting at Columbia to Clayton St. got 100% duplicate feeder infrastructure so they didn't have to touch Ashmont at all during construction. This makes the Red Line a hell of a lot more efficient, reliable, and less maintenance-intensive to consolidate that much from Columbia to where 2 branches run above/below the same roof.
All of this gets messed if MassHighway does the stupid zipper-extension plan and has to start overpassing the OC tracks to carve out still more induced demand space on the highway. Double the cost because of the difficulty of burying a stretch of RR vs. stretch of Red Line, and the MPO renderings don't even make sense and were probably never vetted by a real transit engineer.
So...you want commuter rail fixed sooner than later, keep it simple stupid (MassDOT). And perhaps get yourselves whacked upside the head with reams of data underscoring how little HOV capacity truly matters and how much regulation interstate design standards
do.
